An examination of the phonatory and speech motor control characteristics of patients with spasmodic dysphonia is being conducted to develop a model of the neurological processes involved in this disorder. Three studies have been completed. Patient characteristics predictive of benefit from unilateral surgical resection of the recurrent laryngeal nerve (RLN), were identified. The results suggested two subtypes of this syndrome with only patients with one subtype considered as good candidates for surgical section. In another study, experimental tasks assessing control over phonatory gestures controlled by the RLN, and others controlled by the superior laryngeal nerve were administered to 8 patients. Only tasks involving the RLN were impaired in comparison with normal. Laryngographic signals demonstrated excessive prephonatory changes in laryngeal height and vocal fold movements prior to phonation in patients. The third study compared laryngeal control pre- and post RLN resection. Abnormal prephonatory laryngeal movements persisted post surgical section suggesting that the movement disorder was unaltered. An ongoing study of timing and coordination of respiratory movements prior to the onset of phonation is aimed at determining whether this is an upper motor neuron disorder affecting the coordination and timing of both laryngeal and respiratory movements. A double blind crossover study of Buspirone for the treatment of this disorder is ongoing.